According to Delo, light is considered among the most important elements of automotive design and differentiation these days. Microlens arrays are a key player in these developments. They project LED light, which sits behind a very short focal length, providing sharp images and individual geometries. These systems are increasingly being used as optics in headlights and projection systems due to their low required installation depth.
For increased efficiency, such microlenses are often made of optically pure polymers, in other words, adhesives. The microlens arrays are then fixed to a housing.
With a high viscosity of 75,000 mPa·s, the new Delo Photobond OB4189 is said to enable a high enough aspect ratio for the bonding process. The adhesive thereby retains its shape after dispensing and does not flow, which is important for bonding microlens arrays. It is also claimed to be resistant to yellowing, as shown by life cycle simulations of 500 hours at 140 °C.
The modified acrylate is solvent-free and developed for a temperature application range of -40 °C to +120 °C. It has a compressive shear strength of 30 MPa on polycarbonate and 25 MPa on PMMA. It can be cured with UV light (365 nm) and visible light (400 nm). The typical exposure time at 400 nm with a layer thickness of 100 μm is 5 seconds. This enables high-precision active alignment processes for optical components and low cycle times in automated production.
Christoph Appel, product manager – LED (automotive) at Delo, said: "With Delo Photobond OB4189, we added a high-viscosity and extremely yellowing-resistant product to our portfolio of temperature and humidity-resistant active alignment adhesives that is precisely tailored to the requirements of microlens arrays.”